Devices and methods for digital watermarking

Abstract

An apparatus for embedding a message bit sequence in a video stream is disclosed. The apparatus is configured to determine one or more transformation frames of the at least one frame of the plurality of frames of the video stream based on a wavelet kernel filter. Moreover, the apparatus is configured to encode the message bit sequence by performing for each bit of the message bit sequence a pointwise multiplication of absolute values of the elements of subframes of the one or more transformation frames, depending on the value of the respective message bit of the message bit sequence, with the elements of a first encoding matrix or the elements of a second encoding matrix for obtaining one or more modified transformation frames.

What is claimed is: 
     
         1 . A data processing apparatus for embedding a message bit sequence in a video stream comprising a plurality of frames, wherein the data processing apparatus comprises:
 a processing circuitry configured to modify at least one frame of the plurality of frames of the video stream by:   determining one or more transformation frames of the at least one frame of the plurality of frames of the video stream based on a wavelet kernel filter;   encoding the message bit sequence by performing for each bit of the message bit sequence a pointwise multiplication of absolute values of the elements of subframes of the one or more transformation frames, depending on the value of the respective message bit of the message bit sequence, with the elements of a first encoding matrix or the elements of a second encoding matrix for obtaining one or more modified transformation frames; and   adding the one or more modified transformation frames to the at least one frame of the plurality of frames of the video stream for embedding the message bit sequence in the at least one frame of the plurality of frames of the video stream.   
     
     
         2 . The data processing apparatus of  claim 1 , wherein the processing circuitry is configured to determine the one or more transformation frames of the at least one frame of the plurality of frames of the video stream based on the wavelet kernel filter by performing a convolution of the wavelet kernel filter along one or more directions of the at least one frame of the plurality of frames of the video stream. 
     
     
         3 . The data processing apparatus of  claim 2 , wherein the processing circuitry is configured to determine the one or more transformation frames by a convolution of the wavelet kernel filter along a horizontal direction of the at least one frame, a convolution of the wavelet kernel filter along at least one of a vertical direction of the at least one frame or a convolution of the wavelet kernel filter along a diagonal direction of the at least one frame. 
     
     
         4 . The data processing apparatus of  claim 1 , wherein the video stream comprises a YUV video stream and wherein the at least one frame of the plurality of frames of the YUV video stream is a Y frame. 
     
     
         5 . The data processing apparatus of  claim 1 , wherein the processing circuitry is further configured to downscale the at least one frame of the plurality of frames of the video stream for obtaining a downscaled version of the at least one frame of the plurality of frames of the video stream and to modify the downscaled version of the at least one frame of the plurality of frames of the video stream. 
     
     
         6 . The data processing apparatus of  claim 5 , wherein the processing circuitry is configured to downscale the at least one frame of the plurality of frames of the video stream for obtaining a downscaled version of the at least one frame of the plurality of frames of the video stream by a factor of 2 or more. 
     
     
         7 . The data processing apparatus of  claim 5 , wherein the processing circuitry is further configured to upscale a downscaled version of the one or more modified transformation frames for adding the modified transformation frame to the at least one frame of the plurality of frames of the video stream for embedding the message bit sequence in the at least one frame of the plurality of frames of the video stream. 
     
     
         8 . The data processing apparatus of  claim 1 , wherein the elements of the first encoding matrix have the values +1 or −1 and wherein the second encoding matrix is the result of a pointwise multiplication of the elements of the first encoding matrix with −1. 
     
     
         9 . The data processing apparatus of  claim 8 , wherein the processing circuitry is configured to generate at least one of the first encoding matrix or the second encoding matrix based on a random number generator. 
     
     
         10 . The data processing apparatus of  claim 9 , wherein the processing circuitry is configured to generate at least one of the first encoding matrix or the second encoding matrix to have at least one of a desired spatial frequency distribution or a desired degree of orthogonality. 
     
     
         11 . The data processing apparatus of  claim 1 , wherein the processing circuitry is further configured to multiply at least some of the elements of the one or more modified transformation frames with a scaling factor smaller than 1, before adding the one or more modified transformation frames to the at least one frame of the plurality of frames of the video stream for embedding the message bit sequence in the at least one frame of the plurality of frames of the video stream. 
     
     
         12 . A method for embedding a message bit sequence in a video stream comprising a plurality of frames, wherein the method comprises:
 determining one or more transformation frames of at least one frame of the plurality of frames of the video stream based on a wavelet kernel filter;   encoding the message bit sequence by performing for each bit of the message bit sequence a pointwise multiplication of absolute values of the elements of subframes of the one or more transformation frames, depending on the value of the respective message bit of the message bit sequence, with the elements of a first encoding matrix or the elements of a second encoding matrix for obtaining one or more modified transformation frames; and   adding the one or more modified transformation frames to the at least one frame of the plurality of frames of the video stream for embedding the message bit sequence in the at least one frame of the plurality of frames of the video stream.   
     
     
         13 . A data processing apparatus for decoding a message bit sequence from a video stream comprising a plurality of frames, wherein the data processing apparatus comprises:
 a processing circuitry configured to decode the message bit sequence from at least one frame of the plurality of frames of the video stream by:   determining one or more transformation frames of the at least one frame of the plurality of frames of the video stream based on a wavelet kernel filter;   determining a composite transformation frame based on the one or more transformation frames or a sum of the one or more transformation frames;   decoding the message bit sequence from the composite transformation frame by determining for one or more subframes of the composite transformation frame a first correlation value with a first encoding matrix and a second correlation value with a second encoding matrix and determining the message bit sequence based on the first correlation value and the second correlation value for each of the one or more subframes of the composite transformation frame.   
     
     
         14 . The data processing apparatus of  claim 13 , wherein the processing circuitry is configured to determine the one or more transformation frames of the at least one frame of the plurality of frames of the video stream based on the wavelet kernel filter by performing a convolution of the wavelet kernel filter along one or more directions of the at least one frame of the plurality of frames of the video stream. 
     
     
         15 . The data processing apparatus of  claim 13 , wherein the processing circuitry is configured to determine the one or more transformation frames by a convolution of the wavelet kernel filter along a horizontal direction of the at least one frame, a convolution of the wavelet kernel filter along at least one of a vertical direction of the at least one frame or a convolution of the wavelet kernel filter along a diagonal direction of the at least one frame. 
     
     
         16 . The data processing apparatus of  claim 13 , wherein the video stream comprises a YUV video stream and wherein the at least one frame of the plurality of frames of the YUV video stream is a Y frame. 
     
     
         17 . The data processing apparatus of  claim 13 , wherein the elements of the first encoding matrix have the values +1 or −1 and wherein the second encoding matrix is the result of a pointwise multiplication of the elements of the first encoding matrix with −1. 
     
     
         18 . The data processing apparatus of  claim 17 , wherein the processing circuitry is configured to generate at least one of the first encoding matrix or the second encoding matrix or to receive at least one of the first encoding matrix or the second encoding matrix from an apparatus for encoding the message bit sequence in the video stream based on at least one of the first encoding matrix or the second encoding matrix. 
     
     
         19 . The data processing apparatus of  claim 18 , wherein the processing circuitry is configured to generate at least one of the first encoding matrix or the second encoding matrix to have at least one pf a desired spatial frequency distribution or a desired degree of orthogonality.